Coexistence of medium chain acyl-CoA dehydrogenase deficiency (MCADD) and type 1 diabetes (T1D): a management challenge

Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is an autosomal recessive fatty acid β-oxidation defect. The enzyme, medium chain acyl-CoA dehydrogenase is important in the breakdown of medium chain fats into acetyl-CoA to produce ketones. Ketones are used as an alternative energy source when glucose or hepatic glycogen stores become depleted during prolonged fasting. In MCADD during periods of fasting or acute illness, there are insufficient ketones to compensate for the glucose energy deficit, resulting in an hypoketotic hypoglycaemia alongside a build-up of fatty acids. This build-up of fatty acids can be neurotoxic and lead to altered brain function and even unexpected death. Management includes avoiding prolonged periods of starvation, consuming high carbohydrate drinks during periods of illness and in symptomatic patients, reversal of catabolism and sustained anabolism by provision of simple carbohydrates by mouth or intravenously. Coexistence of MCADD and type 1 diabetes (T1D) is rare, there is no causal association though there are some documented cases. A key goal of management in T1D is achievement of good glycaemic control to reduce risk of long-term complications. This can in some cases increase the risk of hypoglycaemia which can be catastrophic in the presence of MCAD

Detection of hepatocyte nuclear factor 4A(HNF4A) gene variant as the cause for congenital hyperinsulinism leads to revision of the diagnosis of the mother

ObjectivesCongenital Hyperinsulinism (CHI) is the most common cause of persistent hypoketotic hypoglycaemia in neonates and infants. It is a genetic disorder with both familial and sporadic forms.Case PresentationIn this study, we examined two unrelated infants of diabetic mothers (IDMs) presented with HH. DNA sequencing (Sanger and NGS panel) identified pathogenic variants of the Hepatocyte Nuclear Factor 4A (HNF4A) gene in both families. Pathogenic variants of HNF4A gene are reported to cause HH in the newborn period and Maturity Onset Diabetes of the Young (MODY) later in life. The diagnosis of MODY was made in retrospect for the two mothers, thus improving the management of their diabetes.ConclusionGenetic testing for CHI is strongly recommended if neonatal hypoglycemia persists. A family history of MODY or presumed type II diabetes can support that the affected gene is HNF4A.

MON-111 Plasma Insulin Measured with a Sensitive Immunoassay May Establish the Diagnosis of Congenital Hyperinsulinism Without Further Testing

Background: The diagnosis of congenital hyperinsulinism (CHI) is often hampered by a plasma insulin (p-insulin) detection limit of 2-3 mU/L (14-21 pmol/L) by RIA methods. Objective: To evaluate the diagnostic performance of a sensitive immunoassay for p-insulin and to find the optimal p-insulin cut-off for CHI versus other conditions with hypoglycaemia. Design: Single centre retrospective cohort study. Methods: Diagnostic tests with no medication, no i.v. glucose and under fasting conditions were performed in children with a clinical diagnosis of CHI. P-insulin concentrations determined at simultaneous p-glucose concentrations at least <3.2 mmol/L (57.5 mg/dL) were included in the analysis (n=61). The diagnosis of CHI was either clinical (n=61) or by gold standard criteria: hypoketotic hypoglycaemia plus disease-causing genetic mutations and/or diffuse, focal or atypical pancreatic histopathology (n=57). Samples from 15 children with idiopathic ketotic hypoglycaemia (IKH, diagnosis by exclusion, p-ketones >1.5 mmol/L during hypoglycaemia) were used as controls. P-insulin was measured by the high-sensitive assay (Cobas e411 immunoassay analyzer); lower detection limit 1.4 pmol/L (0.2 mU/L); normal range 18-173 pmol/L (2.57-24.7 mU/L). Concentrations <18 pmol/L were considered suppressed; ≥18 pmol/L un-suppressed. Receiver operating characteristics (ROC) curves with determination of area under the curve (AUC) values were performed for the diagnostic performance of p-insulin in the diagnosis of CHI. Results: In the 61 samples from CHI patients, the median (range) p-insulin was un-suppressed in all diagnostic samples [90; 20-758 pmol/L (12.9; 2.9-109.1 mU/L)], while p-insulin was suppressed in all 15 samples from IKH patients [1.5; 1.5-9 pmol/L (0.21; 0.21-1.3 mU/L)]. The ROC AUC was 1.0 (95%CI. 1.0-1.0) for the diagnosis of CHI defined both by the clinic and by gold standard. The optimal p-insulin cut-off was 14.5 pmol/L (2.1 mU/L) or 12.5 pmol/L (1.8 mU/L), for CHI patients by use of a simultaneous p-glucose cut-off of <3.2 mmol/L (57.5 mg/dL; n=61), or 3.0 mmol/L (55 mg/dL; n=49), respectively. Conclusions: The sensitive insulin assay performed excellent in diagnosing CHI with a ROC AUC of 1.0. The use of a p-insulin cut-off of 13 pmol/L (1.86 mU/L) during a diagnostic hypoketotic hypoglycaemia test may establish the diagnosis of CHI without further diagnostic testing.

Hypoinsulinaemic, hypoketotic hypoglycaemia due to mosaic genetic activation of PI3-kinase

Objective Genetic activation of the insulin signal-transducing kinase AKT2 causes syndromic hypoketotic hypoglycaemia without elevated insulin. Mosaic activating mutations in class 1A phospatidylinositol-3-kinase (PI3K), upstream from AKT2 in insulin signalling, are known to cause segmental overgrowth, but the metabolic consequences have not been systematically reported. We assess the metabolic phenotype of 22 patients with mosaic activating mutations affecting PI3K, thereby providing new insight into the metabolic function of this complex node in insulin signal transduction. Methods Three patients with megalencephaly, diffuse asymmetric overgrowth, hypoketotic, hypoinsulinaemic hypoglycaemia and no AKT2 mutation underwent further genetic, clinical and metabolic investigation. Signalling in dermal fibroblasts from one patient and efficacy of the mTOR inhibitor Sirolimus on pathway activation were examined. Finally, the metabolic profile of a cohort of 19 further patients with mosaic activating mutations in PI3K was assessed. Results In the first three patients, mosaic mutations in PIK3CA (p.Gly118Asp or p.Glu726Lys) or PIK3R2 (p.Gly373Arg) were found. In different tissue samples available from one patient, the PIK3CA p.Glu726Lys mutation was present at burdens from 24% to 42%, with the highest level in the liver. Dermal fibroblasts showed increased basal AKT phosphorylation which was potently suppressed by Sirolimus. Nineteen further patients with mosaic mutations in PIK3CA had neither clinical nor biochemical evidence of hypoglycaemia. Conclusions Mosaic mutations activating class 1A PI3K cause severe non-ketotic hypoglycaemia in a subset of patients, with the metabolic phenotype presumably related to the extent of mosaicism within the liver. mTOR or PI3K inhibitors offer the prospect for future therapy.

Carnitine Palmitoyl Tranferase Type 1 Deficiency in Fatty acid oxidation disorder: A Case report

Carnitine palmitoyltransferase 1(CPT-1) catalyzes the formation of acylcarnitine, which is the first step in the oxidation of long chain fatty acid in the mitochondria. CPT-1 deficiency is an inborn error of metabolism. Reported patient with CPT -1 deficiency was a 16 months old boy present with hypoketotic hypoglycaemia, hepatomegaly with raised liver transaminases, hyperamminaemia, convulsion and unconsciousness. Diagnosis was established by IMD panel study. Treatment was done by correction of hypoglycemia, avoidance of hypoglycemia by ensuring frequent feeding, avoidance of prolonged fasting, treatment of infection & other supportive measures.J Shaheed Suhrawardy Med Coll, June 2014, Vol.6(1); 38-40